The present invention relates to an optical subassembly, and particularly to a hermetically sealed optical subassembly, and a method of assembling the same.
In an optical communication system, components on the transmission side are typically packaged in a transmitter optical subassembly (TOSA). While assembling a TOSA, optical transmitting elements (e.g., vertical cavity surface emitting lasers (VCSELs)) are aligned with optical fibers so as to provide sufficient coupling efficiency. The optical transmitting elements and the optical fibers may also need to be aligned with lenses disposed therebetween. It is often difficult to align all of the optical components to each other since a three dimensional alignment, in which these components are aligned in a Z-direction as well as X and Y directions, is typically required.
In addition, when moisture and/or other gases are allowed to enter a TOSA, they can damage the optical transmitting elements and/or other components enclosed therein. Since polymers are generally not gas hermetic, encapsulation may not be sufficient to provide effective hermiticity to keep out moisture and other gases.
One embodiment of the present invention includes a hermetically sealed TOSA for a VCSEL array. In another embodiment, a method of assembling a TOSA is provided. In this embodiment, alignment in the Z-direction between a fiber stub assembly (FSA) and a VCSEL array is performed substantially independently of alignment in the X-Y direction.
In an exemplary embodiment according to the present invention, an optical subassembly is provided. The optical subassembly comprises a ceramic substrate comprising at least one layer having an electrically conductive portion; a metallic plate mounted on the ceramic substrate, the metallic plate having a cavity disposed therethrough; at least one optoelectronic device mounted on the metallic plate proximate the cavity, wherein said at least one optoelectronic device is electrically coupled to the ceramic substrate though the cavity; a lens frame having a receptacle and at least one first alignment means; a lens assembly capable of being coupled to the receptacle, said lens assembly comprising a lens array including at least one lens optically aligned with said at least one optoelectronic device; an alignment plate having a cavity disposed therethrough and at least one second alignment means arranged for cooperatively engaging the first alignment means; and a retainer mounted on the alignment plate for retaining a fiber stub assembly.
Although described herein with respect to an exemplary TOSA, it will be appreciated by those of ordinary skill in the art that the principles disclosed herein may be applied to receiver optical subassemblies (ROSAs) as well.